The present invention relates to a method and apparatus for manufacturing medical devices, in general and to a method and apparatus for manufacturing medical support devices, in particular.
Medical support devices are known in the art. An artery support device is also called a stent. Methods for manufacturing stents are known in the art. U.S. Pat. No. 5,767,480, to Anglin et al, is directed to a hole generation and lead forming for integrated circuit lead frames using laser machining.
U.S. Pat. No. 5,073,694 to Tessier et al, is directed to a method and apparatus for laser cutting a hollow metal workpiece. The method provides for the cutting of the hollow metal workpiece while minimizing or eliminating residue adherence to the inner circumference of the workpiece. Coolant is pumped through the apparatus to contact the inner portion of the workpiece before and during laser cutting.
U.S. Pat. No. 5,345,057 to Muller, is directed to a method of cutting an aperture in a device by means of a laser beam.
U.S. Pat. No. 5,780,807 to Saunders, is directed to a method and apparatus for direct laser cutting of metal stents. The expandable stent is made from a single length of tubing and utilizes direct laser cutting from a single metal tube using a finely focused laser beam. The stent may be made in a variety of ways, but the preferred method provides for cutting a thin-walled tubular member of materials such as stainless steel in order to remove portions of the tubing and give a desired pattern. This is done by utilizing a laser beam.
U.S. Pat. No. 5,707,385 to Williams, is directed to a drug loaded elastic membrane comprising an expandable sheath for delivering a therapeutic drug in a body lumen. The expandable membrane has a first layer and a second layer, which are joined along their edges to form a fluid-tight seal. Before joining the layers, a plurality of apertures are formed in the first layer by known methods such as using a laser.
U.S. Pat. No. 5,843,117 to Alt et al, is directed to an implantable vascular and endoluminal stent and the process of fabricating the same. Tube-type stent is fabricated from tubing with longitudinally oriented struts interconnected by bars or bridges, which define a plurality of through-holes in the wall of the tube. This multiplicity of through-holes is cut by a laser beam.
U.S. Pat. No. 5,531,741 to Barbacci, is directed to illuminate stents which are designed as an improved light emitting device. The stent is formed by extruding a length of tubing and then followed by molding and shaping. Drainage openings are formed in one step of the process. These holes may be made by piercing the wall of the tubing by utilizing a sharpened cutter or by use of a laser.
Electromagnetic forming (EMF) is known in the art. In general, this method is used to form, cut, pierce, and join metals having relatively high electrical conductivity, such as copper, mild alloy, aluminum, low-carbon steel, brass, and molybdenum. The EMF process uses a capacitor bank, a forming coil, a field shaper (mandrel), and an electrically conductive workpiece to create intense magnetic fields that are used to do useful work. This intense magnetic field, produced by the discharge of a bank of capacitors into a forming coil, lasts only a few microseconds. The resulting eddy currents that are induced in a conductive workpiece that is placed close to the coil, then interact with the magnetic field to cause mutual repulsion between the workpiece and the forming coil. The force of this repulsion is sufficient to stress the work metal beyond its yield strength, resulting in a permanent deformation. The magnetic field rapidly accelerates the workpiece against the mandrel, thus forming it to the desired shape. Because the actual forming takes place in a matter of a few microseconds, the high strain rate forming does not affect the material properties in an adverse way. The pressure induced on the workpiece, is comparable to that encountered in mechanical forming of similar parts.
EMF can be usually applied to five forming methods: compression, expansion, contour forming, punching and joining. It is used to expand, compress, or form tubular shapes, to form a flat sheet, and to combine several forming and assembly operations into a single step. It is used in single-step assembly of metal parts to each other or to other components, such as in electrical cables, and joining of aluminum and copper. Highly resistant metals such as titanium, need special EMF equipment, which operate at higher frequencies in the range of 20 to 100kHz.
Because the material is loaded into its plastic region, the springback often associated with mechanical forming, is virtually absent in electroformed parts. Joints made by EMF process are typically stronger than the parent material, and compared to other joining methods, such as laser welding. Assemblies using metal parts formed onto plastics, composites, rubber, and ceramics are also common.
More information regarding EMF can be found in the following references: V. S. Balanethiram, Xiaoyu Hu, Marina Altynova and Glenn S. Daehn, xe2x80x9cHigh Velocity forming: Is it Time to Rediscover This Technologyxe2x80x9d, Engineering Research Center Report ERC/NSM-S-94-15, The Ohio State University, Columbus, OH, 1994, PP. 36-37, V. S. Balanethiram, Xiaoyu Hu, Marina Altynova and Glenn S. Daehn, xe2x80x9cHyperplasticity: Enhanced Formability at High Ratesxe2x80x9d, Journal of Materials Processing Technology, Vol. 45, 1994, pp. 595-600, G. S. Daehn, M. Altynova, V. S. Balanethiram, G. Fenton, M. Padmanabhan, A. Tamhane, and E. Winnard, xe2x80x9cHigh-Velocity Metal Formingxe2x80x94An Old Technology Addresses New Problemsxe2x80x9d, JOM, Vol. 7, July 1995, pp. 42-45, and Metals Handbook, 9thEdition, Volume 14, Forming and Forging, ASM Electromagnetic Forming International, Metals Park, Ohio, pp. 644-653.
It is an object of the present invention to provide a novel method or manufacturing medical support devices, which overcomes the disadvantages of the prior art.
It is an object of the present invention to provide a novel method for manufacturing metal medical devices, while maintaining their original characteristics, which overcomes the disadvantages of the prior art.
In accordance with the present invention, there is thus provided a method for producing a medical support device from at least one object, using an electromagnetic field generator. The method includes the steps of: placing a forming mandrel against the at least one object in the vicinity of a predetermined formation area, and applying at least one electromagnetic field on the formation area, thereby forming the shape of the at least one object.
The method can further include the steps of determining the formation area on the object and repeating from the step of determining, so that additional formation areas define a final shape for the at least one object, the final shape being generally cylindrical.
According to one aspect of the present invention, the object has a tubular shape. In this case, the forming mandrel includes at least one opening, wherein the step of determining includes positioning a selected one of the openings underneath a selected one of the formation areas. Hence, the result of the step of applying an electromagnetic field is punching of material within the selected formation area.
According to another aspect of the invention, the tubular object is made of a material, which can be selected from families of shape memory materials, super elastic materials, stainless steel, alloys, polymeric materials, biocompatible materials, and the like. Accordingly, method can further include a preliminary step of applying shape memory characteristics to the tubular object. Alternatively, the method can also include a final step of applying shape memory characteristics to the tubular object.
In accordance with another preferred embodiment of the present invention, there is thus provided a method for producing a medical support device from a hollow tubular object. The method include the steps of: placing a predetermined mandrel against each of a plurality of formation areas, and applying at least one electromagnetic field on each of the formation areas, thereby forming the tubular object at each of the formation areas.
The method can further include a step of determining the formation area on the object. The mandrel can include at least one opening, in which case, the step of placing, includes positioning of a selected one of the openings underneath a selected one of the formation areas. Hence, the step of applying the electromagnetic field causes punching of material within the selected formation area.
The tubular object can be made of shape memory material. The method can further include a preliminary step of applying shape memory characteristics to the tubular object. Alternatively, the method can further include a final step of applying shape memory characteristics to the tubular object.
According to a further aspect of the invention, the above at least one object can include a plurality of wires. Thus, the formation area is defined by an overlap intersection of at least two of the wires. For example, the method can further include a step of placing the wires in a crosswise structure.
It is noted that at least selected ones of the wires can be straight or curved. These wires can be made of any of the above list of materials, and treated accordingly, before or after formation.
In accordance with a further preferred embodiment of the present invention, there is provided a medical support device, which includes a tubular object. The tubular object includes a plurality of openings, wherein at least selected ones of the openings were electromagnetically formed. This tubular object can be is made of any of the above list of materials
In accordance with a further preferred embodiment of the present invention, there is provided a medical support device, which includes a sheet of conductive material. The sheet of conductive material is folded so as to provide a tubular object, where one edge of the sheet of conductive material overlaps the other, thereby defining an overlapping section. The overlapping edges are joined by means of electromagnetic forming. This medical support device can further include a plurality of openings, where at least some of them were formed according to EMF or according to conventional forming techniques such as drilling, laser cutting, chemical etching, fluid punching, electrical discharge machining, chemical machining, photochemical blanking, abrasive material flow machining, ultrasonic machining, hydrodynamic machining, stamping, and the like.
The sheet of conductive material can be made of any of he above listed materials. The method can have a preliminary or a final step of applying shape memory characteristics to the sheet of conductive material.
In accordance with another preferred embodiment of the present invention, there is provided a medical support device, which includes a sheet of conductive material. The sheet of conductive material includes a plurality of openings, which are formed by electromagnetic forming. The sheet of conductive material is folded so as to provide a tubular object, where one edge of the sheet of conductive material overlaps the other, thereby defining an overlapping section.
The joining of the overlapping edges within the overlapping section can be made using EMF or by conventional techniques such as arc welding, gas welding, resistance welding, soldering, brazing, electron beam welding, laser beam welding, friction welding, diffusion bonding, explosive welding, adhesive bonding, and the like.
In accordance with a further preferred embodiment of the present invention, there is provided a method for producing a medical support device from a sheet of formable material. The method includes the steps of: placing a predetermined mandrel against a plurality of formation areas, and applying at least one electromagnetic field on each of the formation areas, thereby forming the sheet at each of the formation areas. The method can further include a step of determining the formation area on the object.
The mandrel can include at least one opening. In this case the step of placing includes positioning a selected one of the openings underneath a selected one of the formation areas. Hence, the step of applying the electromagnetic fields causes shearing of material within the selected formation area.
The sheet of formable material is made of any of the above materials.
The method can further include a step of folding the sheet of formable material, thereby producing a tubular object.
According to one aspect of the invention, at least selected ones of the formation areas are located in overlapping sections of the sheet of formable material, the overlapping sections being defined in the step of folding.
Depending on various considerations, which arise from the physical organ to be treated, the formable material can either be electrically conductive or not electrically conductive.
In accordance with a further preferred embodiment of the present invention, there is provided a method for producing a medical support device including the steps of: placing a plurality of wires wherein at least a section of each of the wires overlaps a section of at least another of the wires, each of the overlapping section defining an intersection area, and applying at least one electromagnetic field on the overlapping wires of each of the intersection area, thereby joining each of the wires at the intersection area.
The method can further include a step of repeating the step of applying, thereby forming a mesh like structure of the wires. The method can also include a step of folding the mesh, thereby forming a cylinder.
The wires can be generally straight or curved. The arrangement of the wires can be crosswise. At least selected ones of the wires can be made of shape memory alloy, or any of the above listed materials.
In accordance with a further preferred embodiment of the present invention, there is provided a medical support device, which includes a plurality of wires. Each of the wires intersects with at least another of the wires, thereby defining a plurality of intersection points, thereby forming a mesh, where the mesh is folded to in the shape of a cylinder. At least selected ones of the intersecting wires are joined to the wires intersecting therewith, by means of electromagnetic forming process.